Two expressions are equivalent when they name the same number for every value of the letter. Beans in rectangles show why: 3 rows of (x + 2) is 3x + 6, the distributive property. Like terms combine, y + y + y = 3y, and a common factor can be pulled out, 6x + 9 = 3(2x + 3). Linear expressions add and subtract term by term, even with fraction coefficients. The crew builds bean rectangles at the Puzzle Post and tests every claim with values.